Induction motors typically include a stator having a bore within which a rotor is disposed. The stator comprises teeth distributed uniformly over its inner wall and separated by notches. The teeth support coils, which extend into the notches. The coils allow the establishment of a rotating magnetic field causing rotation of the rotor. The assembly of the coils forms the winding.
It is desirable that the motors to be housed in actuators for home automation applications emit the least possible noise for user comfort. The noise originates from the vibrations inside the motor. The vibrations are generally caused by the clearances between the components of the motor, including rotor eccentricity in the stator bore.
Furthermore, part of the winding conventionally projects beyond the ends of the stator. These projections are called winding heads or coil ends. Their deterioration, during or after assembly, due in particular to the axial abutment of a component against the stator, may cause motor malfunction. It is, therefore, important to protect the coil ends for motor reliability. It is known to protect the coil ends, for example with a protection element which prevents their contact with the rotor shaft. However, the presence of said protection element tends to move away the bearings used to ensure the rotation of the rotor. It can therefore increase eccentricity. Other assembly restraints can maintain bearings on both sides of the protection elements.
In particular, it is known from patent document EP2237396 a tubular induction motor with two directions of rotation contained in a tube of a tubular actuator intended to be installed in a building, said motor comprising a rotor supported by bearings and a stator comprising a bundle of plates forming a central bore and centered in the tube, wherein a bearing support part is centered in the central bore, and wherein the bearing is smooth and conductive, and disposed the closest possible to a short-circuit ring of the rotor, less than 2 mm or 1 mm.
However, the bearings are arranged at a distance from the stator. However one has to keep in mind that the farther away the bearings are from the stator, the greater is the risk of rotor eccentricity. Rotor eccentricity can cause vibrations and, as a consequence, noise, during operation.
Moreover, the bearings are arranged in a bearing support part, which itself abuts against the stator. There is therefore, in addition to a clearance between the bearing support part and the stator, a clearance between the support part and the bearing it supports. This multitude of clearances in the tolerance stack-up contributes to the generation of vibrations during operation.
Furthermore, it is known from patent document EP0410933 a tubular double insulation gear motor comprising a motor consisting of a stator secured to a metal tube and a rotor driving a gearbox. It further comprises a tubular insulating casing arranged between the stator and the tube. The stator is fitted with end pieces having a portion of smaller diameter than that of the stator and around which the insulating casing is axially locked.
However, here too, the bearings of the gear motor described in patent document EP0410933 are arranged at a distance from the stator. Therefore, the distance between said two bearings is relatively large. Such a distance may cause a problem of rotor eccentricity. In operation, rotor eccentricity generates vibration and, as a result, noise.